The hindered amines have long been recognized as light and/or as thermal stabilizers for a host of organic materials subject to degradation induced by oxygen, heat or actinic light. The patent and academic publication literature is replete with references to these hindered amine compounds and their valuable stabilizing efficacies. There is no mention or suggestion in any of such references that the hindered amines themselves are also flame retardants per se.
Particularly relevant are U.S. Pat. Nos. 5,004,770; 5,096,950; 5,204,473; 5,300,544; 5,844,026; 6,117,995 and 6,271,377. These references pertain to various N-hydrocarbyloxy substituted hindered amines (so called NOR and NOROL hindered amines) and to various compositions stabilized therewith. As mentioned above, none of these reference disclose or even hint that the compositions stabilized with the NOR or NOROL hindered amines alone are flame retardant. This inherent property was never discovered, not even serendipitously, until the present invention was made. That this is so, is in itself evidence that even those of considerable skill in the hindered amine stabilizer art were quite surprised by this unexpected discovery. The fact that a large amount of an inorganic or organic classical bromine and/or phosphorus containing flame retardant could be substituted by a small amount of a NOR or NOROL hindered amine and still achieve very acceptable flame retardancy was also quite unexpected. This is highly beneficial for the environment and for safety reasons. Accordingly, polymeric substrate compositions made flame retardant by incorporating therein a synergistic mixture of a NOR or NOROL hindered amine plus a classic inorganic or organic bromine and/or phosphorus containing flame retardant is also quite surprising, unexpected and dearly not obvious to those of skill in this stabilizer art. This invention affords the public a valuable method for flame retarding polymers which cannot be gleaned from any of the prior art references.
U.S. Pat. No. 5,393,812 does describe polyolefin compositions which are made flame retardant by a combination of a halogenated hydrocarbyl phosphate or phosphonate ester flame retardant in combination with a alkoxyamine functional hindered amine, but there is no suggestion that the hindered amine itself is responsible for the flame retardancy, but rather that the hindered amine is preventing delustering and other undesirable effects from occurring in these polyolefin compositions.
European Application No. 0 792 911 A2, published after the filing date of the parent provisional application Serial No. 60/051,331, discloses that alkoxyamine functional hindered amines may have some flame retarding properties, but are quite effective when used to enhance the flame retarding efficacy of tris(trihalogenopentyl) phosphate flame retardants. This publication is somewhat ambivalent as to whether the alkoxyamine functional hindered amine are really themselves flame retardants in the absence of the recognized phosphate flame retardant.
The flame retardant (FR) market today is comprised of products which function to interfere with the combustion process by chemical and/or physical means. Mechanistically these FRs have been proposed to function during combustion of an article in either the gas phase, the condensed phase or both. The organohalogens are proposed to generate halogen species (e.g. HX) which interferes in the gas phase with free radical organic xe2x80x9cfuelxe2x80x9d from the polymer substrate. Synergists are proposed to react with HX to form additional chemical species with interfere with combustion in the gas phase, such as reaction of antimony oxide with HX to form antimony halide and water vapor. Still other flame retardant classes are proposed to impart efficacy in the xe2x80x9ccondensedxe2x80x9d phase such as forming a protective char layer on the polyester, or forming an intumescent or foaming on the polymer surface. The char or intumescent layer is thought either to prevent organic fuel from migrating from the polymer into the vapor phase where it can fuel combustion, or the char can act as a thermal shield to protect the underlying polymer article from thermally induced decomposition and generation of fuel. Phosphorus compound of various classes (e.g. halo- or non-halogenated) are an example. Further still, other classes of compounds are proposed to function in the condensed and/or vapor phase. Metal hydrates or metal oxides are proposed to generate water vapor under thermal conditions, the water acting to dilute the fuel mix in the combustion zone and to remove heat from the flame zone via conversion of water to vapor. Alumina trihydrate, magnesium hydroxide or oxide, and other compounds are reported to function in this way.
These state of the art chemistries described above have various detrimental aspects in addition to the effective flame retarding attributes mentioned. Certain organobrominated compounds are under governmental scrutiny for the generation of toxic by-products during the production or combustion such as dioxanes from polybrominated diphenyl oxides. Certain metal-containing flame retardants, notably antimony oxides, are under scrutiny for worker exposure and toxicity reasons. Antimony oxides often contain trace amounts of arsenic compounds which are suspected cancinogens. Overall, a growing concern has arisen regarding the generation of smoke and toxic gases which are evolved from these flame retardants during a fire. While the classic FRs may be effective combustion suppressants, the toxic gases they form pose a threat to human exposure.
The instant invention alleviates some of the detrimental aspects of the current state of the art which the use of large amounts of commercial flame retardants pose. The instant NOR or NOROL hindered amines are non-halogenated and free of heavy metals, thus avoiding generation of corrosive HX gases and avoiding exposure to toxic metals. In some applications, the instant invention provides a direct replacement for current FR systems where the instant NOR or NOROL hindered amine compounds provide a complimentary enhancment or synergistic system for heavy metals (e.g. antimony oxide replacement in ABS) where good flame retardancy can be achieved by using less classic FR agent in the presence of the instant NOR or NOROL hindered amine compound.
The instant invention pertains to a flame retardant composition which comprises
(a) a polymer substrate, preferably a polyolefin, most preferably polypropylene, and
(b) an effective flame retarding amount of a synergistic mixture of
(i) a hindered amine of formula A: 
xe2x80x83wherein
E is alkoxy of 1 to 18 carbon atoms, cycloalkoxy of 5 to 12 carbon atoms or aralkoxy of 7 to 15 carbon atoms, or E is xe2x80x94Oxe2x80x94Txe2x80x94(OH)b, preferably E is methyoxy, propoxy, cydohexyloxy or octyloxy, most preferably cyclohexyloxy,
T is a straight or branched chain alkylene of 1 to 18 carbon atoms, cycloalkylene of 5 to 18 carbon atoms, cycloalkenylene of 5 to 18 carbon atoms, a straight or branched chain alkylene of 1 to 4 carbon atoms substituted by phenyl or by phenyl substituted by one or two alkyl groups of 1 to 4 carbon atoms;
b is 1, 2 or 3 with the proviso that b cannot exceed the number of carbon atoms in T, and when b is 2 or 3, each hydroxyl group is attached to a different carbon atoms of T;
R is hydrogen or methyl,
m is 1 to 4,
when m is 1,
R2 is hydrogen, C1-C18alkyl or said alkyl optionally interrupted by one or more oxygen atoms, C2-C12alkenyl, C6-C18aryl, C7-C18aralkyl, glycidyl, a monovalent acyl radical of an aliphatic,cycloaliphatic or aromatic carboxylic acid, or a carbamic acid, preferably an acyl radical of an aliphatic carboxylic acid having 2-18 C atoms, of a cycloaliphatic carboxylic acid having 5-12 C atoms or of an aromatic carboxylic acid having 7-15 C atoms or: 
xe2x80x83wherein x is 0 or 1; 
xe2x80x83wherein y is 2-4;
when m is 2,
R2 is C1 -C12alkylene, C4-C12alkenylene, xylylene, a divalent acyl radical of an aliphatic, cytioaliphatic, araliphatic or aromatic dicarboxylic acid or of a dicarbamic acid, preferably an acyl radical of an aliphatic dicarboxylic acid having 2-18 C atoms, of a cycloaliphatic or aromatic dicarboxylic acid having 8-14 C atoms, or of an aliphatic, cydoaliphatic or aromatic dicarbamic acid having 8-14 C atoms: 
wherein D1 and D2 are independently hydrogen, an alkyl radical containing up to 8 carbon atoms, an aryl or aralkyl radical including 3,5-di-t-butyl-4hydroxybenzyl radical, D3 is hydrogen, or an alkyl or alkenyl radical containing up to 18 carbon atoms, and d is 0-20;
when m is 3, R2 is a trivalent acyl radical of an aliphatic, unsaturated aliphatic, cycloaliphatic, or aromatic tricarboxylic acid;
when m is 4, R2 is a tetravalent acyl radical of a saturated or unsaturated aliphatic or aromatic tetracarboxylic acid including 1,2,3,4-butanetetracarboxylic acid, 1,2,3,4-but-2-ene-tetracarboxylic, and 1,2,3,5- and 1,2,4,5pentanetetracarboxylic acid; or
wherein the hindered amine compound is a mixture of N,Nxe2x80x2,Nxe2x80x2xe2x80x3-tris{2,4-bis[(1-hydrocarbyloxy-2,2,6,6-tetramethylpiperidin-4-yl)alkylamino]-s-triazin-6-yl}-3,3xe2x80x2-ethylenediiminodipropylamine; N, Nxe2x80x2, Nxe2x80x2xe2x80x3-tris{2,4-bis[(1-hydrocarbyloxy-2,2,6,6-tetramethylpiperidin-4-yl) alkyl-amino]-s-triazin-6-yl}-3,3xe2x80x2-ethylenediiminodipropylamine, and bridged derivatives as described by formulas I, II, IIA and III:
R1NHxe2x80x94CH2CH2CH2NR2CH2CH2NR3CH2CH2CH2NHR4xe2x80x83xe2x80x83(I)
T-E1-T1xe2x80x83xe2x80x83(II)
T-E1xe2x80x83xe2x80x83(IIA)
G-E1-G1-E1-G2xe2x80x83xe2x80x83(III)
where in the tetraamine of formula I:
R1 and R2 are the s-triazine moiety E2; and one of R3 and R4 is the s-triazine moiety E2 with the other of R3 or R4 being hydrogen,
E2is: 
R is methyl, propyl, cyclohexyl or octyl, preferably cyclohexyl,
R5 is alkyl of 1 to 12 carbon atoms, preferably n-butyl,
where in the compound of formula II or IIA when R is propyl, cyclohexyl or octyl,
T and T1 are each a substituted by R1-R4 as is defined for formula I, where
(1) one of the s-triazine moieties E2 in each tetraamine is replaced by the group E1 which forms a bridge between two tetraamines T and T1,
E1 is: 
xe2x80x83or
(2) the group E1 can have both termini in the same tetraamine T as in formula IIA where two of the E2 moieties of the tetraamine are replaced by one E1 group, or
(3) all three s-triazine substituents of tetraamine T can be E1 such that one E1 links T and T1 and a second E1 has both termini in tetraamine T,
L is propanediyl, cyclohexanediyl or octanediyl;
where in the compound of formula III:
G,G1 and G2 are each tetraamines substituted by R1-R4 as defined for formula I, except that G and G2 each have one of the s-triazine moieties E2 replaced by E1, and G1 has two of the triazine moieties E2 replaced by E1, so that there is a bridge between G and G1 and a second bridge between G1 and G2; 
which mixture is prepared by reacting two to four equivalents of 2,4-bis[(1-hydrocarbyl-oxy-2,2,6,6-piperidin-4-yl)butylamino]-6-chloro-s-triazine with one equivalent of N,Nxe2x80x2-bis(3-aminopropyl)ethylenediamine;
or the hindered amine is a compound of the formula IIIb: 
in which the index n ranges from 1 to 15;
R12 is C2-C12alkylene, C4-C12alkenylene, C5-C7cycloalkylene, C5-C7 cycloalkylene-di(C1-C4alkylene), C1-C4alkylenedi(C5-C7cycoalkylene), phenylenedi(C1-C4alkylene) or C4-C12alkylene interrupted by 1,4piperazinediyl, xe2x80x94Oxe2x80x94 or  greater than Nxe2x80x94X1 with X1 being C1-C12acyl or (C1-C12alkoxy)carbonyl or having one of the definitions of R14 given below except hydrogen; or
R12 is a group of the formula (Ibxe2x80x2) or (Icxe2x80x2): 
with m being 2 or 3,
X2 being C1-C18alkyl, C5-C12cycloalkyl which is unsubstituted or substituted by 1, 2 or 3 C1-C4alkyl, phenyl which is unsubstituted or substituted by 1, 2 or 3 C1-C4alkyl or C1-C4alkoxy; C7-C9phenylalkyl which is unsubstituted or substituted on the phenyl by 1, 2 or 3 C1-C4alkyl; and
the radicals X3 being independently of one another C2-C12alkylene;
R13 R14 and R15, which are identical or different, are hydrogen, C1-C18alkyl, C5-C12cycloalky which is unsubstituted or substituted by 1, 2 or 3 C1-C4alkyl; C3-C18alkenyl, phenyl which is unsubstituted or substituted by 1, 2 or 3 C1-C4alkyl or C1-C4alkoxy; C7-C9phenylalkyl which is unsubstituted or substituted on the phenyl by 1, 2 or 3 C1-C4alkyl; tetrahydrofurfuryl or C2-C4alkyl which is substituted in the 2, 3 or 4 position by xe2x80x94OH, C1-C8alkoxy, di(C1-C4alkyl)amino or a group of the formula (lexe2x80x2): 
with Y being xe2x80x94Oxe2x80x94, xe2x80x94CH2xe2x80x94, xe2x80x94CH2CH2xe2x80x94 or  greater than Nxe2x80x94CH3, or xe2x80x94N(R14)(R15) is additionally a group of the formula (lexe2x80x2); the radicals A are independently of one another xe2x80x94OR13,xe2x80x94N(R14)(R15) or a group of the formula (IIId): 
xe2x80x83X is xe2x80x94Oxe2x80x94 or  greater than Nxe2x80x94R16, 
xe2x80x83R16 hydrogen, C1-C18alkyl, C3-C18alkenyl, C5-C12cycloalkyl which is unsubstituted or substituted by 1, 2 or 3 C1-C4alkyl; C7-C9phenylalkyl which is unsubstituted or substituted on the phenyl by 1, 2 or 3 C1-C4alkyl; tetrahydrofurfuryl, a group of the formula (IIIf): 
xe2x80x83or C2-C4alkyl which is substituted in the 2, 3 or 4 position by xe2x80x94OH, C1-C8alkoxy, di(C1-C4alkyl)amino or a group of the formula (lexe2x80x2);
xe2x80x83R11 has one of the definitions given for R16; and the radicals B have independently of one another one of the definitions given for A;
(ii) a brominated and/or a phosphorus containing flame retardant with the proviso that when the polymeric substrate is polypropylene, the flame retardant is not a halogenated hydrocarbyl phosphate or phosphonate.
Preferably the hindered amine compounds are the mixture of compounds of formula I, II, IIA and III where R is cyclohexyl; bis(1-octyloxy-2,2,6,6tetramethylpiperidin-4-yl) sebacate; 1-(2-hydroxy-2-methylpropoxy)-4-octadecanoyloxy-2,2,6,6-tetramethylpiperidine, or the compound of formula: 
In the structures A to R, if any substituents are C1-C18 alkyl, they are for example methyl, ethyl, n-propyl, n-butyl, sec-butyl, tert-butyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-hexadecyl or n-octadecyl. Typical cycloalkyl groups include cyclopentyl and cydohexyl; typical cycloalkenyl groups include cyclohexenyl; while typical aralkyl groups include benzyl, alpha-methyl-benzyl, alpha, alpha-dimethylbenzyl or phenethyl. C1-C12 alkyl and cyclohexyl are preferred.
If R2 is a monovalent acyl radical of a carboxylic acid, it is for example an acyl radical of acetic acid, stearic acid, salicydic acid, benzoic acid or xcex2-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid.
If R2 is a divalent acyl radical of a dicarboxylic acid, it is for example an acyl radical of oxalic acid, adipic acid, succinic acid, suberic acid, sebacic acid, phthalic acid dibutylmalonic acid, dibenzylmalonic acid or butyl-(3,5-di-tert-butyl-4-hydropxybenzyl)-malonic acid, or bicydoheptenedicarboxylic acid, with succinates, sebacates, phthalates and isophthalates being preferred.
If R2 is a divalent acyl radical of a dicarbamic acid, it is for example an acyl radical of hexamethylenedicarbamic acid or of 2,4-toluylenedicarbamic acid.
The instant NOR hindered amine compounds as described above are known in the prior art and are prepared as taught in U.S. Pat. Nos. 5,004,770; 5,096,950; 5,204,473, 5,300,544; 5,844026; 6,117,995; and 6,271,377.
Preferably, the polymer substrate is selected from the group of resins consisting of the polyolefins, the thermoplastic olefins, styrenic polymers and copolymers, and ABS.
More preferably, the polymer substrate is polypropylene, polyethylene, thermoplastic olefin (TPO), ABS and high impact polystyrene.
Most preferably, polymer substrate is polypropylene, polyethylene or thermoplastic olefin (TPO).
Preferably, the NOR or NOROL hindered amine of component (i) is
(a) the mixture of compounds of formula I, II, IIA and III where R is cyclohexyl;
(b) 1-cydohexyloxy-2,2,6,6-tetramethyl-4-octadecylaminopiperidine;
(c) bis(1-octyloxy-2,2,6,6-tetramethylpiperidin-4-yl) sebacate;
(d) 2,4-bis[(1-cydohexyloxy-2,2,6,6-tetramethylpipeddin-4-yl)butylamino]-6-(2-hydroxy-ethylamino-s-triazine;
(e) bis(1-cydohexyloxy-2,2,6,6tetramethylpiperidin-4yl) adipate;
(f) the oligomeric compound which is the condensation product of 4,4xe2x80x2-hexamethylene-bis(amino-2,2,6,6-tetramethylpiperidine) and 2,4-dichloro-6-[(1-octyloxy-2,2,6,6-tetramethyl-piperidin-4-yl)butylamino]-s-triazine end-capped with 2-chloro4,6-bis(dibutylamino)-s-triazine;
(g) the oligomeric compound which is the condensation product of 4,4xe2x80x2-hexamethylene-bis(amino-2,2,6,6-tetramethylpiperidine) and 2,4-dichloro-6-[(1-cyclohexyloxy-2,2,6-tetra-methylpiperidin-4-yl)butylamino]-s-triazine end-capped with 2-chloro-4,6-bis(dibutylamino)-s-triazine;
(h) 2,4bis[(1-cydohexyloxy-2,2,6,6-piperidin-4-yl)butylamino]-6-chloro-s-triazine;
(i) 1-(2-hydroxy-2-methylpropoxy)-4-octadecanoyloxy-2,2,6,6-tetramethylpiperidine; or
(j) the compound of formula: 
Most preferably, the compound of component (i) is:
(a) the mixture of compounds of formula I, II, IIA and III where R is cyclohexyl;
(c) bis(1-octyloxy-2,2,6,6-tetramethylpiperidin-4-yl) sebacate;
(i) 1-(2-hydroxy-2-methylpropoxy)-4-octadecanoyloxy-2,2,6,6-tetramethylpiperidine; or
(j) the compound of formula: 
The effective flame retarding amount of the hindered amine is that needed to show flame retarding efficacy as measured by one of the standard methods used to assess flame retardancy. These include the NFPA 701 Standard Methods of Fire Tests for Flame-Resistant Textiles and Films, 1989 and 1996 editions; the UL 94 Test for Flammability of Plastic Materials for Parts in Devices and Appliances, 5th Edition, Oct. 29, 1996; Limiting Oxygen Index (LOI), ASTM D-2863; and Cone Calorimetry, ASTM E-1354.
The effective amount of hindered amine needed to achieve flame retardancy is from 0.05 to 10% by weight based on the polymeric substrate; preferably 0.5 to 8% by weight; and most preferably 0.5 to 2% by weight.
The effective flame retarding amount of the synergistic mixture (b) containing components (i) and (ii) is 0.5 to 30% by weight based on component (a).
In that synergistic mixture (b), the effective flame retarding amount of a hindered amine is 0.5 to 10% by weight based on component (a); and preferably is 0.5 to 8% by weight based on component (a).
More particularly, the flame retardant compounds useful in the instant invention are preferably selected from the group consisting of
polybrominated diphenyl oxide (DE-60F, Great Lakes Corp.)
decabromodiphenyl oxide (DBDPO; SAYTEX(copyright) 102E)
bis(2,3-dibromopropyl ether) of bisphenol A (PE68),
ammonium polyphosphate (APP) or (HOSTAFLAM(copyright) AP750),
brominated epoxy resin,
ethylene-bis(tetrabromophthalimide) (BT93),
1,2-bis(tribromophenoxy)ethane (FF680), and
tetrabmmo-bisphenol A (SAYTEXW RB(copyright) 100).